I don't like flip-top plastic boxes, and absolutely despise the slide-top plastic boxes.
I own some of each, and I'll continue using them until they die.
But I won't buy any more, and I turn them down when people offer them to me for free.
I've had too many crack, break, or otherwise go to crap.
Bags were used frequently in my early years reloading, but I got tired of just having a "pile" of ammo in my range bag or ammo can, and the complications that come with trying to stack bags of ammo on shelves.
Now...
Most of my ammo is stored and transported in recycled or scrounged factory boxes, or National Metallic (
MidwayUSA CB-series) boxes -- styrofoam tray in a plain white cardboard box.
The only real exceptions are 9mm and .223 (when I have enough loaded). The majority of that ammo gets stored in bulk in double-corrugated cardboard boxes (former cast bullet shipping boxes) until it's time to refill the 20-round and 50-round factory-style boxes.
For storage, the best advise I can give is NEVER touch the brass/ammo with bare fingers once it's cleaned.
Skin oil is corrosive and will corrode the bullets/brass in a day or two.
Minor staining is only a problem for people that want to win beauty contests with their ammo.
I don't care. I just need ammo that works.
My sweat is not 99% acetic acid.
I have ammo from the '80s that I loaded. It has fingerprints and staining from lube residue. It'll be fine for another 20 years -- and even that limit is just my estimate of when the powder is likely to show signs of degradation.